Lateral lithospheric conductivity patterns,from European synchronous observatory data

Much information on the regional lithospheric structure may come from MTS data acquired by synchronous 2D arrays and processed with regard to the nonlocal response of a laterally inhomogeneous subsurface. We suggest to invert the nonlocal MT responses applying correlation of all surface horizontal and vertical components of the geomagnetic field recorded simultaneously at all stations. The inversion algorithm has been applied to 2004–2005 European observatory data of diurnal S_q variations for first five harmonics and yielded lateral conductivity patterns for different periods. The maps show spatial correlation between conductivity maxima and lithospheric thickness minima and, specifically, highlight the contours of the Pannonian basin, where lithosphere is as thin as ～50 km, from seismic data.     

Evidence for the volcanoclastic genesis of the Carnian diamondiferous bed in the Ust’-Olenek area (from petrographic and geochemical data)

A detailed petrographic study of a 0.4–1.2 m thick Carnian diamondiferous bed of the Angardam-Tasa Ridge (Ust’-Olenek area, northern Siberia) was performed. It showed that the bed earlier referred to as a terrigenous deposit might be interpreted as an intensely altered volcanoclastic lapilli tuff of basic and, probably, ultrabasic composition. The tuff occurs within a 100 m thick Ladinian–Carnian volcanosedimentary sequence. It consists mainly of resurgent material: altered lithoclasts (nodules of basic-ultrabasic? lithology), devitrified volcanic glass, fragments of autolithic breccia, etc. The thin volcanoclastic sheet is supposed to have formed within a sedimentation basin as a result of phreatomagmatic eruptions of kimberlite volcanoes. The substantiation of the volcanogenic origin of the Carnian diamondiferous bed might be a new approach to elucidate the primary source of widespread placer diamonds in Arctic Siberia.     

厦门东海域鱼类食物网研究

本文分析了厦门东海域58种鱼类的营养关系.根据对它们的食性分析,并依其食料生物的生态类群,将厦门东海域的鱼类食性类型分为:浮游生物食性、底栖生物食性、游泳动物食性、浮游生物和底栖生物、底栖生物和游泳动物食性等5种.该海域鱼类的营养级可分为4级:杂食性鱼类、低级肉食性鱼类、中级肉食性鱼类和高级肉食性鱼类,其中低级肉食性鱼类占优势,为63.79%.本文还分析了厦门东海域鱼类的食物网及其能量流动途径,并提出合理利用和保护厦门东海域鱼类资源的建议.     

准噶尔盆地复杂地区地层压力预测方法研究及应用

准噶尔盆地地层压力分布复杂,长期以来由于地层压力预测不准,在钻井过程中常出现井壁失稳、卡钻、井壁坍塌、钻井液漏失等工程事故,严重影响了钻井速度.为减少工程复杂问题,准确预测地层压力至关重要.为此,在准噶尔盆地开展了断层相关褶皱理论解释复杂构造、利用地质构造建模指导速度建模,求出每层的层速度和真倾角,再用Terzaghi 理论计算地层孔隙压力,计算结果证实地层压力预测精度显著提高.     

Crystal Structure and Chemical Composition of Ludwigite from Vranovac Ore Deposit (Boranja Mountain,Serbia)

The crystal structure of ludwigite from Vranovac ore deposit (Boranja Mt., Serbia) was refined using the X-ray powder diffraction (XRPD) Rietveld method in the space group Pbam to a final RB=7.45% and RF=5.26%. It has the unit cell dimensions of: a=9.2515(2) ?; b=12.3109(2) ?; c=3.03712(7) ?; and V=345.91(1) ?3. The calculated distances and angles are mostly in good agreement with the Mg2+-Fe2+ substitutions across the M(1) and M(3) sites, as well as with the Fe3+-Al3+ replacement in the M(4) site. However, the mean observed M(2)-O distance is considerably shorter than prescribed, due to a slight increase of the Fe3+ content in the M(2) site. Such replacement was compensated by slight increase of the Fe2+ content in the M(4) site, resulting in the (Mg1.48Fe2+0.46Fe3+0.05Mn0.02)2.01(Fe3+0.94Fe2+0.04Al0.02)1.00B1.00O5 composition. The formation temperature was estimated to be about 500–600°C. The influences of the various chemical compositions to the crystallographic parameters, M-O distances, M(3) and M(4) sites shift, distortion parameters and estimated valences, were also studied and compared with other reference samples.     

Nonlocal response functions: application to processing BEAR data

It has been suggested that regional array MTS data be processed with an algorithm based on the nonlocal response of laterally heterogeneous subsurface to an arbitrary electromagnetic excitation. The algorithm is tested with synthetic models which show that the inversion quality can be improved by accumulation of information through repeated measurements, at either changing or fixed array configurations. Besides the array configuration, the inversion quality depends on the selected size of the survey area. The choice of the area size defines the inversion conditions in terms of choice between the magnetic and electric mode for correlation of electromagnetic potentials. The algorithm has been applied to data acquired during the BEAR Project in the Fennoscandian shield. Preliminary results indicate a spatial correlation between conductivity minimums and Moho depth maximums. The apparent resistivity maps obtained with the suggested algorithm highlight the boundaries between the Lapland–Kola, Karelia, and Svecofennia tectonic provinces.     

Dissolved oxygen criteria for freshwater fish in New Zealand: a revised approach

Maintenance of suitable conditions in lowland rivers for both fish passage and resident species is crucial to ensuring the long-term sustainability of fish populations. The dissolved oxygen concentration of water is a key factor controlling habitat quality for fish and a critical measure of stream health. Continued land use intensification and greater exploitation of water resources has contributed towards increasing the frequency and duration of low dissolved oxygen events in lowland rivers and the associated risk of adverse effects on fish communities. Revised guidelines are therefore proposed to support setting of biologically relevant dissolved oxygen limits for the protection of New Zealand freshwater fish communities. These guidelines account for both event magnitude and duration, identify different protection levels based on the risk of negative impacts and are based on current scientific knowledge on the tolerances of New Zealand fish species.     

Nonlocal electromagnetic response: Implications in the regional sounding

Due regard was given to the nonlocal electromagnetic responses in the processing of the data of the International Baltic Electromagnetic Array Research (BEAR) 1998 Project. Maps of lateral distributions of the apparent electrical resistivity for different time periods were compiled. In these maps, the main tectonic boundaries between the Lapland-Kola, Karelian, and Svecofennian tectonic provinces within the Baltic Shield appear as zones with reduced apparent electrical resistivity. There is supposedly some correlation between the positions of the maxima in electrical resistivity and the maximum Moho depths. In the same way, the data from the network of geomagnetic observatories in the European region (the INTERMAGNET Project) were processed for 2004–2005, and maps of the laterally inhomogeneous distribution of the apparent resistivity in Europe have been compiled for different time periods. The correlation is observed between the positions of the minima in the electrical resistivity and the minima in the thickness of the lithosphere.     

Toxicity assessment of New Zealand and Pacific dinoflagellates Ostreopsis and Gambierdiscus (Dinophyceae) extracts using bioassays

The dinoflagellate genus Ostreopsis produces palytoxin-like compounds (PLTXs) and the genus Gambierdiscus produces ciguatoxins (CTXs) and maitotoxin (MTX). Human illness has been recorded following the consumption of CTX-contaminated finfish. Their effects on the flora and fauna in the environment are largely unexplored. Toxin profiles of extracts of Ostreopsis and Gambierdiscus isolates from the Pacific region were characterised using liquid chromatography tandem mass spectrometry. Sea urchin (Evechinus chloriticus) fertilisation was unaffected by any algal extracts, but extracts containing maitotoxin-3 (MTX-3, but not MTX or CTXs), or with high concentrations of PLTXs, were toxic to urchin larval development. Gambierdiscus extracts containing CTXs elicited toxic responses in zebrafish (Danio rerio) embryo toxicity assays; extracts containing only MTX-3 elicited a limited response. Ostreopsis extracts containing PLTXs caused no response. The results demonstrate potential impacts of toxic dinoflagellates on larval organisms and the potential of embryonic assays as toxicity screening tools.     

Assessment of prediction performances of stochastic models: Monthly groundwater level prediction in Southern Italy

Stochastic modelling of hydrological time series with insufficient length and data gaps is a serious challenge since these problems significantly affect the reliability of statistical models predicting and forecasting skills. In this paper, we proposed a method for searching the seasonal autoregressive integrated moving average(SARIMA) model parameters to predict the behavior of groundwater time series affected by the issues mentioned. Based on the analysis of statistical indices, 8 stations among 44 available within the Campania region(Italy) have been selected as the highest quality measurements. Different SARIMA models, with different autoregressive, moving average and differentiation orders had been used.By reviewing the criteria used to determine the consistency and goodness-of-fit of the model, it is revealed that the model with specific combination of parameters, SARIMA(0,1,3)(0,1,2) _(12), has a high R~2 value,larger than 92%, for each of the 8 selected stations. The same model has also good performances for what concern the forecasting skills, with an average NSE of about 96%. Therefore, this study has the potential to provide a new horizon for the simulation and reconstruction of groundwater time series within the investigated area.